import java.util.Scanner;

class BuyComputer
{
    public static void main(String[] args)
    {
        Scanner scanner = new Scanner(System.in);
        int price = scanner.nextInt();
        int day = 0;
        int sum = 0;
        while (sum < price)
        {
            day++;
            sum += day;
        }
        System.out.println(day);
        scanner.close();
    }
}